1. Field of the Invention
The invention relates to a turbine blade/vane.
2. Brief Description of the Related Art
Such a turbine blade/vane, which has an aerodynamically shaped shell around which flow occurs, is known from DE 198 59 787 A1. This shell has a first side wall and a second side wall, which are connected together at a leading edge at the incident flow end and at a trailing edge at the departing flow end, which extend longitudinally from a blade root to a vane tip and which are connected together between leading edge and trailing edge by a plurality of inner ribs. These ribs form two cooling gas paths on the inside of the turbine blade/vane or on the inside of the shell, which cooling gas paths respectively guide a cooling gas flow from the root to the tip of the turbine blade/vane and, in the process, deflect the cooling gas flow several times in serpentine shape from the outside to the inside and from the inside to the outside.
Such a serpentine shape cooling gas path therefore consists of a sequence of 180° reversal bends. In this arrangement, the ribs are arranged in such a way that, in one cooling gas path in the region of the leading edge and in another cooling gas path in the region of the trailing edge, they protrude inward from the shell and have an angle of approximately 45° relative to the blade/vane root. This produces an intensive retardation of the cooling gas flow, which improves the cooling effect.
Each cooling gas path begins in the blade/vane root and ends at the blade/vane tip, where the cooling gas can emerge through a cover plate arranged at the tip almost exactly into the middle of a hot gas path surrounding the turbine blade/vane.
To the extent that finer and coarser particles are entrained in the cooling gas, these can collect and be deposited in the deflection regions which deflect cooling gas flow in the direction of the blade/vane root. Because of this, a deposit layer can be formed which grows with time and which, as a rule, consists of oxides. This deposit layer usually has a lower thermal conductivity than the shell and the ribs, so that the cooling effect of the cooling gas flow is reduced in this deposit region. Local overheating can, therefore, occur in the regions of the turbine blade/vane affected, with the result that cracks, melting and structural changes can occur in the endangered regions of the blade/vane. Due to the deterioration in cooling caused by deposits, the life of the turbine blade/vane is therefore reduced.